Genetics of individualizing patient care.
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Critical Care↗
Biomedical subjects
Michael R Pinsky
Publications and source records attributed to Michael R Pinsky.
Measuring aortic diameter improves accuracy of esophageal Doppler in assessing fluid responsiveness.
OBJECTIVE: Fluid responsiveness requires the accurate measurement of cardiac output that can be approached by aortic blood flow (ABF) as measured by esophageal Doppler monitoring (EDM). EDM devices may either include an echo-determination of aortic diameter or estimate aortic diameter from nomograms and thus consider it as constant. However, it is unclear if measuring aortic diameter increases the accuracy of EDM to identify fluid responsiveness. Aortic diameter varies with arterial pressure such that its measure could be essential for assessing the changes in ABF during acute circulatory failure. We attempted to demonstrate that measuring aortic diameter improved the accuracy of EDM to assess fluid responsiveness. DESIGN: Prospective study. SETTING: University hospital intensive care unit. PATIENTS: Seventy-six patients with acute circulatory failure in whom a fluid challenge was given. INTERVENTIONS: Rapid volume expansion (500 mL of NaCl 0.9%). MEASUREMENTS AND MAIN RESULTS: We measured aortic velocity and area by EDM before and after fluid loading and evaluated the effects of fluid challenge on ABF, either measured after fluid infusion (measured ABFafter) or estimated assuming an unchanging aortic area (estimated ABFafter). If measured ABFafter was used for assessing fluid response, it was increased above 15% compared with ABF at baseline in 41 patients (responders). Conversely, estimated ABFafter increased above 15% from ABF at baseline in 27 patients only; that is, the effects of the challenge were underestimated in 14 patients. In these 14 patients, the relative change in mean arterial pressure during volume expansion was of greater magnitude than in patients who were classified as nonresponders by considering measured ABFafter. CONCLUSIONS: Monitoring the changes in aortic diameter improves the accuracy of EDM in assessing the hemodynamic effects of a fluid challenge, especially if it induces a large increase in arterial pressure. Estimating rather than measuring the aortic diameter may lead to underestimation of fluid responsiveness.
Aorta, Thoracic↗
Estimating left ventricular contractility using inspiratory-hold maneuvers.
OBJECTIVE: To compare estimates of left ventricular (LV) end-systolic elastance created by inferior vena caval (IVC) occlusion with those by apneic continuous positive airway pressure (CPAP). DESIGN AND SETTING: Prospective interventional study in a university large animal research laboratory. SUBJECTS: Sixteen intact, pentobarbital-anesthetized mongrel male dogs. INTERVENTIONS: Insertion of LV conductance and pressure catheters, then during apnea sequentially performed IVC occlusion and CPAP of 5, 10, and 15 mmHg for 10 s, each interspersed by positive-pressure breathing. In the final 11 dogs runs were repeated during both esmolol (2 mg min-1) and dobutamine (5 microg kg-1 min-1) infusions. MEASUREMENTS: LV pressure-volume relationships during apneic baseline and then as LV end-diastolic volume decreased by each maneuver to calculate LV end-systolic elastance and preload-recruitable stroke work as measures of contractility. RESULTS: End-systolic elastance estimated at 5 mmHg CPAP levels and IVC occlusions were similar while 10 and 15 mmHg CPAP gave different values. However, end-systolic elastance was lower during esmolol infusion and higher during dobutamine for all CPAP and IVC occlusion maneuvers. Preload-recruitable stroke work measures were similar across maneuvers. With increasing CPAP the LV filling and end-systolic elastance were progressively shifted upward and to the left, with volume on the x-axis, consistent with an unaccounted for increase in intrathoracic pressure. CONCLUSIONS: The use of 5 mmHg CPAP-induced preload-reduction allows estimation of LV end-systolic elastance and preload-recruitable stroke work in intact dogs. Increasing CPAP to more than 10 mmHg creates estimates of LV contractility that are different but covary with IVC occlusion-derived values.
Animals↗
Informal caregiver burden among survivors of prolonged mechanical ventilation.
RATIONALE: Although caregiver burden is well described in chronic illness, few studies have examined burden among caregivers of survivors of critical illness. In existing studies, it is unclear whether the observed burden is a consequence of critical illness or of preexisting patient illness. OBJECTIVES: To describe 1-yr longitudinal outcomes for caregivers of patients who survived critical illness, and to compare depression risk between caregivers of patients with and without pre-intensive care unit (ICU) functional dependency. METHODS: Prospective, parallel, cohort study of survivors of prolonged (greater than 48 h) mechanical ventilation and their informal caregivers. Caregivers were divided into two cohorts on the basis of whether patients were functionally independent (n = 99, 59%), or dependent (n = 70, 41%) before admission. Functional dependency was defined as dependency in one or more activities of daily living or in three or more instrumental activities of daily living. Patient and caregiver outcomes were measured 2, 6, and 12 mo after mechanical ventilation initiation. MEASUREMENTS AND MAIN RESULTS: We studied three caregiver outcomes: depression risk, lifestyle disruption, and employment reduction. Most patients were male (59.8%), with a mean (SD) age of 56.6 (19.0) yr. Caregivers were mostly female (75.7%), with a mean (SD) age of 54.6 (14.7) yr. Prevalence of caregiver depression risk was high at all time points (33.9, 30.8, and 22.8%; p = 0.83) and did not vary by patient pre-ICU functional status. Lifestyle disruption and employment reduction were also common and persistent. CONCLUSIONS: Depression symptoms, lifestyle disruption, and employment reduction were common among informal caregivers of critical illness survivors. Depression risk was high regardless of patient pre-ICU functional status.
Caregivers↗
The classical Guyton view that mean systemic pressure, right atrial pressure, and venous resistance govern venous return is/is not correct.
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Atrial Function, Right↗
Ability of pulse contour and esophageal Doppler to estimate rapid changes in stroke volume.
OBJECTIVE: Two technologies to acquire beat-to-beat stroke volume values exist, pulse contour analysis and esophageal Doppler monitoring. Pulse contour analysis assumes fixed aortic impedance. Esophageal Doppler assumes a constant proportional descending aortic flow and diameter. These assumptions may not be correct as arterial tone or myocardial contractility vary. We tested these relationships in the setting of rapidly changing stroke volumes and different cardiovascular states over a period of 10-15 cardiac cycles. DESIGN AND SETTING: In a university research facility we compared beat-to-beat changes in stroke volume as measure by aortic root flow probe or conductance catheter to pulse contour analysis and stroke distance as measured by esophageal Doppler. SUBJECTS: Five purpose-bred research hounds. INTERVENTIONS: To obtain a wide range of rapidly changing stroke volumes measurements were made during transient inferior vena cava occlusion. Data were gathered under baseline conditions and during norepinephrine, nitroprusside, and dobutamine infusions. MEASUREMENTS AND RESULTS: The pulse contour stroke volumes and esophageal Doppler stroke distance paralleled flow probe stroke volumes under all conditions (R(2)=0.89 for all measures). However, the absolute changes and proportional changes and the absolute values for both surrogate measures differed from absolute stroke volumes. Bland-Altman analysis showed no consistent bias or degree of precision across all animals under any given cardiovascular state. CONCLUSIONS: Both pulse contour stroke volumes and esophageal Doppler derived stroke distance estimates yield significant correlations with aortic root flow probe. However, the absolute values, absolute changes, or proportional changes may not reflect actual stroke volumes as cardiovascular state varies, making their use in estimating absolute changes in stroke volume potentially inaccurate.
Animals↗
Effects of radial left ventricular dyssynchrony on cardiac performance using quantitative tissue Doppler radial strain imaging.
Our objective was to test the hypothesis that novel angle-corrected radial strain imaging can quantify left ventricular dyssynchrony associated with contractile impairment and improved with biventricular pacing. Eight open-chest dogs were studied by novel angle-corrected color-coded radial strain imaging and high-fidelity pressure-conductance catheters recording pressure-volume loops. Heart rate was controlled by right atrial pacing and all timing intervals were corrected by R-R interval (corrected interval = measured interval/(R-R interval)(1/2)). Left bundle branch block, simulated by right ventricular free wall pacing, resulted in marked radial dyssynchrony, which we defined as maximal time difference between peak segmental strain, from 39 +/- 17 to 354 +/- 49 milliseconds and stroke work decreased from 157 +/- 40 to 60 +/- 37 mJ, (P < .005 vs baseline). Depression of contractility by high-dose esmolol (end-systolic pressure-volume relationship from 5.7 +/- 2.4 to 3.6 +/- 1.0 mm Hg/mL) was associated with augmented dyssynchrony to 388 +/- 53 milliseconds (P < .05 vs baseline right ventricular pacing). Biventricular pacing improved dyssynchrony to 55 +/- 19 milliseconds and stroke work to 143 +/- 33 mJ (P < .05 vs right ventricular pacing). Changes in radial dyssynchrony correlated significantly with 6-site average regional strain (r = -0.93 +/- 0.05 individually, r = 0.80 overall) and stroke work (r = -0.88 +/- 0.12 individually, r = -0.82 overall). Angle-corrected radial strain imaging has clinical potential to quantify mechanical dyssynchrony and effects of biventricular pacing.
Animals↗
Practical issues of hemodynamic monitoring at the bedside.
The hemodynamic monitoring of a surgical patient acquires a major relevance in high-risk patients and those suffering from surgical diseases associated with hemodynamic instability, such as hemorrhagic or septic shock. This article reviews the fundamental physiologic principles needed to understand hemodynamic monitoring at the bedside. Monitoring defines stability, instability, and response to therapy. The major hemodynamic parameters measured and derived from invasive hemodynamic monitoring, such as arterial, central venous, and pulmonary catheterization, are discussed, as are its clinical indications, benefits, and complications. The current clinical data relevant to hemodynamic monitoring are reviewed and discussed.
Blood Pressure↗
Passive leg raising predicts fluid responsiveness in the critically ill.
OBJECTIVE: Passive leg raising (PLR) represents a "self-volume challenge" that could predict fluid response and might be useful when the respiratory variation of stroke volume cannot be used for that purpose. We hypothesized that the hemodynamic response to PLR predicts fluid responsiveness in mechanically ventilated patients. DESIGN: Prospective study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: We investigated 71 mechanically ventilated patients considered for volume expansion. Thirty-one patients had spontaneous breathing activity and/or arrhythmias. INTERVENTIONS: We assessed hemodynamic status at baseline, after PLR, and after volume expansion (500 mL NaCl 0.9% infusion over 10 mins). MEASUREMENTS AND MAIN RESULTS: We recorded aortic blood flow using esophageal Doppler and arterial pulse pressure. We calculated the respiratory variation of pulse pressure in patients without arrhythmias. In 37 patients (responders), aortic blood flow increased by > or =15% after fluid infusion. A PLR increase of aortic blood flow > or =10% predicted fluid responsiveness with a sensitivity of 97% and a specificity of 94%. A PLR increase of pulse pressure > or =12% predicted volume responsiveness with significantly lower sensitivity (60%) and specificity (85%). In 30 patients without arrhythmias or spontaneous breathing, a respiratory variation in pulse pressure > or =12% was of similar predictive value as was PLR increases in aortic blood flow (sensitivity of 88% and specificity of 93%). In patients with spontaneous breathing activity, the specificity of respiratory variations in pulse pressure was poor (46%). CONCLUSIONS: The changes in aortic blood flow induced by PLR predict preload responsiveness in ventilated patients, whereas with arrhythmias and spontaneous breathing activity, respiratory variations of arterial pulse pressure poorly predict preload responsiveness.
Aorta↗
Hemodynamic monitoring over the past 10 years.
Changes in hemodynamic monitoring over the past 10 years have followed two paths. First, there has been a progressive decrease in invasive monitoring, most notably a reduction in the use of the pulmonary artery catheter because of a presumed lack of efficacy in its use in the management of critically ill patients, with an increased use of less invasive monitoring requiring only central venous and arterial catheterization to derive the same data. Second, numerous clinical trials have documented improved outcome and decreased costs when early goal-directed protocolized therapies are used in appropriate patient populations, such as patients with septic shock presenting to Emergency Departments and high-risk surgical patients before surgery (pre-optimization) and immediately after surgery (post-optimization). Novel monitoring will be driven more by its role in improving outcomes than in the technical abilities of the manufacturers.
Blood Circulation↗
Evidence-based review of the use of the pulmonary artery catheter: impact data and complications.
The pulmonary artery catheter (PAC) was introduced in 1971 for the assessment of heart function at the bedside. Since then it has generated much enthusiasm and controversy regarding the benefits and potential harms caused by this invasive form of hemodynamic monitoring. This review discusses all clinical studies conducted during the past 30 years, in intensive care unit settings or post mortem, on the impact of the PAC on outcomes and complications resulting from the procedure. Although most of the historical observational studies and randomized clinical trials also looked at PAC-related complications among their end-points, we opted to review the data under two main topics: the impact of PAC on clinical outcomes and cost-effectiveness, and the major complications related to the use of the PAC.
Catheterization, Swan-Ganz↗
Second International Conference on Rapid Response System and Medical Emergency Team, 28-30 June 2006, Pittsburgh, PA, USA.
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Emergency Medical Services↗
Modeling ischemia-induced dyssynchronous myocardial contraction.
Left ventricular (LV) contraction dyssynchrony is not easily quantified. We previously described a model for quantifying LV dyssynchrony that referenced regional amplitude and phase angles to global LV systole using esmolol-induced regional dyskinesis. We tested the hypothesis that our sine wave model and phase angle analysis of regional dyssynchrony in a canine model could also assess dyssynchrony of contraction during regional ischemia. Hence we compared intracoronary esmolol and matched regional ischemia in 10 anesthetized open-chest dogs. Regional and total LV volumes (conductance catheter), piezoelectric crystal shortening, and LV pressures were measured before, during, and after esmolol-induced apical dyskinesis and matched regional ischemia. We defined regional phase angle of contraction (alpha) as the relative distance, measured in degrees, that regional minimal volume differed from global end-systole. We also compared maximal stroke volume (SV), observed effective SV (that portion of regional SV contributing to total SV for each treatment), and calculated effective SV (total regional SV x cosine alpha). Dobutamine infusion increased homogeneity of regional alpha relative to baseline. Both esmolol and ischemia significantly delayed (P < 0.05) apical contraction as quantified by increased alpha (12.4 degrees +/- 28.1 degrees to 27.4 degrees +/- 30.4 degrees and 54.2 degrees +/- 32.6 degrees , respectively) (mean +/- sd) and decreased regional effective SV (4.7 +/- 2.5 mL to 3.6 +/- 2.2 mL and 4 +/- 2.5 mL, respectively) relative to baseline. Our study indicates that intracoronary esmolol and ischemia induced qualitatively similar mechanical effects on myocardial function and that a sine wave model to estimate regional effective SV is a sensitive method to detect and quantify regional dyssynchrony induced by ischemia. Potentially, phase angle and regional amplitude analyses may prove to be effective measures to identify and quantify the beneficial effects of resynchronization therapies on myocardial function.
Animals↗
The effect of tracheal gas insufflation on gas exchange efficiency.
Transtracheal gas insufflation (TGI) improves gas exchange efficiency, but is associated with hyperinflation, and usually requires ventilator adjustment to compensate for the increased gas flow. Although bidirectional TGI (Bi-TGI) minimizes hyperinflation, it does not preclude the need to reduce tidal volumes to prevent hyperinflation. A flow-compensation system was developed by Respironics (Murrysville, PA) to match TGI flows; however, neither that nor the efficacy of Bi-TGI have been tested in vivo. We tested the hypotheses that flow compensation allows for a constant minute ventilation; Bi-TGI produces less hyperinflation than does unidirectional TGI (Uni-TGI), and endotracheal tube size influences the degree of hyperinflation during TGI. Seven anesthetized intact dogs were studied during positive-pressure ventilation using the Respironics flow compensation system. Measurements were made during steady-state conditions at constant and measured levels of CO(2) production. Gas exchange efficiency (assessed by expired gas analysis for dead space) and hyperinflation (measured as an increase in pleural pressure) were compared during Bi- and Uni-TGI and for endotracheal tube sizes varying from 7 to 10F. Bi- and Uni-TGI could be delivered at constant minute ventilation without adjusting ventilatory setting when the flow compensation circuit was present. Uni-TGI produced more hyperinflation than did Bi-TGI with all sizes of endotracheal tube, and hyperinflation was universally present as tube size decreased to 7.5F. We conclude that this new flow compensation system allows for the delivery of TGI without the need for adjustments to the ventilator settings, and that Bi-TGI produces less hyperinflation than does Uni-TGI, even with small diameter endotracheal tubes.
Animals↗
Intensive care and emergency medicine: progress over the past 25 years.
Over the last quarter of a century, intensive care medicine has developed into an established hospital specialty with its own unique identity and characteristics. Significant advances have occurred, mostly in a succession of small steps rather than any dramatic leap, with many being linked to advances in health care across other disciplines. In addition, many changes have resulted from the scientific identification of the detrimental effects of certain traditional practices once thought to be therapeutic. Here, in an attempt to learn from the past and offer guidance for future progress, we detail some of the key changes in various aspects of intensive care medicine including respiratory, cardiovascular, metabolic, and nutritional care, as well as sepsis, polytrauma, organization, and management.
Cardiovascular Diseases↗
Effects of modulation of left ventricular contractile state and loading conditions on tissue Doppler myocardial performance index.
The Tei index is clinically useful to quantify left ventricular (LV) function, but it requires sequential Doppler recordings from two different views. A related myocardial performance index (MPI) using tissue Doppler (TD) can be rapidly calculated from a single beat; however, its ability to quantify contractility and the effects of acute changes in loading have not been determined. Our aim was to test the hypothesis that TD MPI can quantify contractile state but is affected by acute alterations in loading, using LV pressure-volume relations in an animal model. Eight dogs were studied by using mitral annular TD, high-fidelity pressure, and conductance catheters. TD MPI was calculated as (a' - b')/b', where a' was the duration of mitral annular velocity during diastole and b' was the duration of the systolic wave. End-systolic elastance (Ees), the time constant of isovolumic relaxation (tau), and peak positive and negative first derivative of pressure (dP/dtmax and dP/dtmin, respectively) were used as measures of LV function. Data were obtained at baseline, at dobutamine and esmolol infusion to alter contractile state, and at inferior vena cava and aortic occlusion to alter preload and afterload. TD MPI decreased from 0.83 (SD 0.19) to 0.62 (SD 0.20) with dobutamine and increased to 1.19 (SD 0.26) with esmolol. TD MPI significantly correlated with dP/dtmax (r = -0.76), Ees (r = -0.68), dP/dtmin (r = 0.82), and tau (r = 0.78); however, it was affected by acute decreases in preload [from 0.83 (SD 0.19) to 1.09 (SD 0.36)] and acute increases in afterload [to 1.23 (SD 0.17)]. All the above increases and decreases and r values were significant (P < 0.05 vs. baseline). In conclusion, TD MPI can rapidly quantify alterations in LV contractile state but is affected by acute alterations in preload and afterload.
Animals↗
Functional hemodynamic monitoring.
Hemodynamic monitoring is a central component of intensive care. Patterns of hemodynamic variables often suggest cardiogenic, hypovolemic, obstructive, or distributive (septic) etiologies to cardiovascular insufficiency, thus defining the specific treatments required. Monitoring increases in invasiveness, as required, as the risk for cardiovascular instability-induced morbidity increases because of the need to define more accurately the diagnosis and monitor the response to therapy. Monitoring is also context specific: requirements during cardiac surgery will be different from those in the intensive care unit or emergency department. Solitary hemodynamic values are useful as threshold monitors (e.g. hypotension is always pathological, central venous pressure is only elevated in disease). Some hemodynamic values can only be interpreted relative to metabolic demand, whereas others have multiple meanings. Functional hemodynamic monitoring implies a therapeutic application, independent of diagnosis such as a therapeutic trial of fluid challenge to assess preload responsiveness. Newer methods for assessing preload responsiveness include monitoring changes in central venous pressure during spontaneous inspiration, and variations in arterial pulse pressure, systolic pressure, and aortic flow variation in response to vena caval collapse during positive pressure ventilation or passive leg raising. Defining preload responsiveness using these functional measures, coupled to treatment protocols, can improve outcome from critical illness. Potentially, as these and newer, less invasive hemodynamic measures are validated, they could be incorporated into such protocolized care in a cost-effective manner.
Blood Pressure Determination↗
Esophageal Doppler monitoring predicts fluid responsiveness in critically ill ventilated patients.
OBJECTIVE: To test whether fluid responsiveness can be predicted by the respiratory variation in aortic blood flow and/or the flow time corrected for heart rate monitored with esophageal Doppler. DESIGN AND SETTING: Prospective study in a 24-bed medical intensive care unit of a university hospital. PATIENTS: 38 mechanically ventilated patients with sinus rhythm and without spontaneous breathing activity in whom volume expansion was planned. INTERVENTIONS: The aortic blood flow was measured using an esophageal Doppler monitoring device before and after fluid infusion (500 ml NaCl 0.9% over 10 min). The variation in aortic blood flow over a respiratory cycle between its minimal and maximal values was calculated. The flow time was also measured. MEASUREMENTS AND RESULTS: Aortic blood flow increased by at least 15% after volume expansion in 20 patients (defined as responders). Before fluid infusion the respiratory variation in aortic flow was higher in responders than in nonresponders (28+/-12% vs. 12+/-5%). It significantly decreased after volume expansion (18+/-11%) in responders only. A respiratory variation in aortic flow before volume expansion of at least 18% predicted fluid responsiveness with a sensitivity of 90% and a specificity of 94%. Flow time increased with fluid infusion in responders and nonresponders. A flow time corrected for heart rate below 277 ms predicted fluid responsiveness with a sensitivity of 55% and a specificity of 94%. The area under the ROC curve generated for variation in aortic blood flow ABF was greater than that generated for flow time. CONCLUSIONS: The respiratory variation in aortic blood flow reliably predicts fluid responsiveness in patients with sinus rhythm and without breathing activity.
Aorta↗